10-story apartment building, decent design and massing, $3 million before shipping and on-site placement, assembled in 1 day

Broad Sustainable Building is at it again with its new 5D folding modular system. in Treehugger, by Lloyd Alter, June 15, 2021, Fact checked by Haley Mast

10-story building
Broad Sustainable Building

Broad Sustainable Building has been developing factory-built structures since 2009, usually with headlines noting a hotel was built in a week or an office tower in a month. However, this is the first time we have ever seen a 10-story building put together in just one day. Watch the video: https://www.treehugger.com/embed?url=https%3A%2F%2Fyoutu.be%2FBgm5ex1q9BU&id=mntl-sc-block_1-0-2-iframe&options=e30%3D (Turn down your sound – for some reason the soundtrack is a version of Scarborough Fair, made famous by Simon and Garfunkel, and it doesn’t work for me)

It is built with the company’s latest 5D system that has the advantages of shipping container housing: It can be transported inexpensively using standard shipping container handling equipment—at least when shipping prices get back to relative normality. But it does not have the hopelessly limiting interior dimensions of shipping containers, because walls and floors fold out to double their width, resulting in a clear span of 39.3 feet by 15.75 feet by 9 feet high. Treehugger has shown this system before, but never in a building this tall.

Assembly of unit
Broad Sustainable Building

This offers the best of both modular and panelized worlds. Because half of the unit is shipped in 3D form, one can have the kitchens, baths, and mechanical systems all in place, without shipping a lot of air for bedrooms and living spaces, which are in the foldout sides. Broad explains:

Floors, walls, windows, and glass; electrical and mechanical equipment; AC and DC power, lighting, water supply, and drainage; as well as sanitary facilities, are all completed in the factory before transport. Because 95% of the producer is preassembled, there is minimal work to be done on site. After bolts are tightly connected, and water supply and drainage among modules and electricity are ready, the structure can be occupied immediately.”

Core of slab
CTS Panel.Broad Sustainable Building

The walls are made of Broad’s CTS Slab panels, a stressed-skin panel made of stainless steel. Treehugger has expressed concerns about this before, given stainless steel is not a particularly green material. Plus, all those tubes would be wonderful thermal bridges transporting heat between the two skins which would act like radiators: it might be structurally strong but a thermal disaster. But Broad’s Daniel Zhang tells Treehugger that it’s not a problem:

The thermal bridging exists, yet the walls of the tubing are so thin, so so far it performs close to structural bearing wood beams, overall. Embodied energy as according to calculations because it is stainless, the life span and recyclability, making the embodied energy over the long term lower than wood, steel, concrete. The strength comes from the higher weight to strength ratio, the little tubes do all the shear wall, compression work.”

Zhang also notes the panels can last thousands of years and the buildings themselves can be “disestablished” or taken apart and moved. All components can be disentangled and upgraded. “5D buildings can be completely folded up and rebuilt in another location, turning the concept of housing from fixed real estate into ‘movable property,'” says Zhang.

I noted in a previous post that this presents interesting opportunities:

“There are many properties that might be vacant for a couple of years where this might work as a rental building in the short term, perhaps for all those workers, teachers, and nurses who can’t afford to live in many expensive cities. You could build them on school parking lots or for that matter, they are so light you could probably plop them on roofs. Because the building can be separated from the land, it dramatically changes the economics of real estate. Or, if the water is rising because of climate change, you can move the whole building inland. This would be an excellent idea for condos in Miami.”

The panel is filled with 10 inches of rock wool and the building is then wrapped in vacuum panels to cover all the thermal bridges of the framing. The windows are triple or quadruple glazed, so it ends up with energy consumption that is “1/5 to 1/10th that of conventional buildings.”

Broad is also in the ventilation business, so there is heat recovery ventilation and filtered fresh air, so that “indoor PM2.5 is 100 times less than outdoors.”

It’s all done in the factory

Broad has developed a series of building systems, and a well-known structural engineer once told Treehugger the only reason these buildings got built so quickly was that Broad threw so many people at them and made them work all night. But the 5B system is built almost entirely in the factory; the only thing done on-site is the unfolding of the walls and making the connections. Engineer Brian Potter of Construction Physics is not thrilled with the B-Core stainless steel panel system, but when it comes to the 5B:

I actually find this system fairly compelling. It’s arranged for long-distance shipping intelligently, maximizing the amount square footage shipped in smart ways (folding) without adding a ton of extra complexity or field work. It doesn’t allow the layout to change for future use, but it is theoretically demountable and movable. It’s highly repetitive, making large-volume production easier – it actually resembles the “kit of parts” idea, an endlessly alluring concept in building design where a relatively small number of basic components gets combined in a variety of building configurations.”

It is indeed compelling, combining the economy of containerized shipping, the 3D configuration of modular construction, and the space-saving benefits of panelized construction, picking and choosing the best of these different systems.

price of a whole building
Broad Sustainable Building

And hey, you can buy an entire 20 unit apartment building for less than the cost of a modest house in San Francisco or Toronto—shipping not included. Who wouldn’t find that compelling?